Methods and system for thermo-optic power monitoring

ABSTRACT

A radiation monitor for a lighting device, and operating methods and systems therefor are provided. In one example, a radiation monitor may include a first sensor receiving radiation output directly from a light-emitting element of the lighting device and radiation output from external sources; and a second sensor receiving the radiation output from the external sources without receiving the radiation output directly from the light-emitting element of the lighting device. The radiation monitor may determine an intensity of the radiation output directly from the light-emitting element based on a difference in the output signals from the first sensor and the second sensor.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional ApplicationNo. 62/734,182 titled “METHODS AND SYSTEM FOR THERMO-OPTIC POWERMONITORING”, and filed on Sep. 20, 2018. The entire contents of theabove-identified application are hereby incorporated by reference forall purposes.

BACKGROUND AND SUMMARY

Accurate monitoring of lighting devices can be difficult because ofextraneous light or radiation from external sources, including lightoutput from the lighting device that is retro-reflected back towards thelighting device. Owing to this incident radiation from external sources,photosensors in a conventional lighting device can indicate higherradiation levels than what is actually output from the lighting device.In cases where the lighting device emits polarized light,retro-reflected radiation incident at the lighting device can bemitigated by employing a beam-splitter or a prism, and obtaining anunperturbed fractional measurement of the incident light. In the absenceof polarization, paired identical light sources can be used to enable anindirect measurement of the light output; with one of the light sourcesspatially separated from the other and provided with an environmentisolated from external light sources.

The inventors herein have recognized potential issues with the aboveapproach. Namely, accuracy and reliability of radiation monitoring ofmore commonplace non-polarized incoherent light sources such as LED orincandescent light sources can be increased. In particular, employingpaired light sources can be highly variable because the ratio of lightfrom multiple sources must remain constant over time and ambientconditions, which often change. Furthermore, paired light sourcesincreases a system complexity and cost since multiple light sources areemployed and monitored.

One approach that at least partially addresses the above issues includesa radiation monitor for a lighting device, comprising a first sensorreceiving radiation output directly from a light-emitting element of thelighting device and radiation output from external sources, a secondsensor receiving the radiation output from the external sources withoutreceiving the radiation output directly from the light-emitting elementof the lighting device, and electronic circuitry receiving outputsignals from the first sensor and the second sensor and determining anintensity of the radiation output directly from the light-emittingelement based on a difference in the output signals from the firstsensor and the second sensor.

In this manner, the technical result of accurate and reliable monitoringof a light source is provided. In particular, the influence of incidentradiation arising from external sources including retro-reflectedradiation, is removed by subtracting its contribution from the measuredradiation. Furthermore, the radiation monitor can be implemented andcustomized to a particular lighting device or application by utilizingdifferent types of radiation sensors. Further still, the radiationmonitoring is provided without paired light sources. In this way, costsand complexity of the radiation monitor can be reduced, while increasingits reliability and accuracy as compared with conventional devices.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustrating a lighting device exposed toradiation from external sources, including retro-reflected radiation.

FIG. 2 is a partial perspective view of a first example of a lightingdevice and sensors of a radiation monitor to monitor output of thelighting device.

FIG. 3 is a partial cross-sectional view of the lighting device and thesensors of the radiation monitor to monitor output of the lightingdevice of FIG. 2.

FIG. 4 is a partial perspective view of a second example of a lightingdevice and sensors of a radiation monitor to monitor output of thelighting device.

FIG. 5 is a perspective view of a sensor mounting block and the sensorsof the radiation monitor to monitor output of the lighting device ofFIG. 4.

FIG. 6 illustrates over-filled and under-filled conditions whenpositioning a sensor of the radiation monitor to monitor output of thelighting device of FIG. 4.

FIG. 7 is a schematic illustrating an example of a lighting system,including a lighting device such as the lighting device of FIG. 2 orFIG. 4, and a radiation monitor such as the radiation monitors of FIG. 2or FIG. 4, respectively.

FIGS. 8-9 are example circuit diagrams for the radiation monitors ofFIGS. 2 and 4, respectively.

FIG. 10 shows voltage response plots for operating a radiation monitorsuch as the radiation monitors of FIG. 2 or FIG. 4.

FIG. 11 is an example flow chart of a method for thermo-optic powermonitoring a lighting device utilizing a radiation monitor such as theradiation monitors of FIG. 2 or FIG. 4.

FIG. 12 is partial cross-sectional view of a radiation monitor and alighting device such as the radiation monitors and lighting devices ofFIG. 4.

FIG. 13 is a partial cross-sectional view illustrating various types oflight capillaries.

DETAILED DESCRIPTION

The present description relates to a radiation monitor, and methods andsystems of radiation monitoring, which increase reliability and accuracyrelative to conventional systems and methods by subtracting incidentradiation from external sources, including retro-reflected radiation.FIG. 1 illustrates how retro-reflective surfaces and retro-reflectedradiation can direct extraneous light back to a lighting device. Aradiation monitor, such as the example apparatus shown in FIGS. 2-3, mayremove retro-reflected radiation, as well as other radiation fromexternal sources, from a measured output of a lighting device. A furtherexample of a radiation monitor that may remove retro-reflected radiationand other radiation from external sources from a measured output of alighting device is illustrated in FIGS. 4-6. The radiation monitor ofFIGS. 4-6 may employ light capillaries, as illustrated in FIG. 12 andFIG. 13. FIG. 7 illustrates a system including a lighting deviceintegrated with a radiation monitor, such as the radiation monitors ofFIGS. 2-6. The radiation monitors of FIGS. 2-6 may be operated accordingto the electronic circuit diagrams depicted in FIGS. 7-8. Removal of theretro-reflected radiation and other radiation from external sources froma measured output of a lighting device during operation of the radiationmonitors is illustrated by the plots in FIG. 10. Furthermore a method ofoperating a radiation monitor and/or a system including a radiationmonitor and a lighting device is illustrated in FIG. 11.

Turning now to FIG. 1, it illustrates a schematic showing a lightingdevice 100, including an array of light-emitting elements 110, and aphotosensor 112. Photosensor 112 may be able to detect radiation outputdirectly from the array of light-emitting elements 110. Light radiation132 is emitted from the array of light-emitting elements 110 parallel toan axis 130 on to a reflective surface 120. Reflective surface 120 mayinclude portions which exhibit retro-reflective properties such thatincident light radiation 132 may be retro-reflected as retro-reflectedradiation 134. Retro-reflected radiation 134 may include retro-reflectedradiation 136 that is reflected back on to the array of light-emittingelements 110 and detected by the photosensor 112. Furthermore, radiation152 and 162 emitted from external sources 150 and 160 respectively, maybe incident at the array of light-emitting elements 110 and detected bythe photosensor 112. Non-limiting examples of external sources 150 and160 may include radiation from sources other than the radiation outputdirectly from the lighting device such as stray light, radiation emittedfrom other lighting devices, retro-reflected light, and the like.

Accordingly, the total radiation measured by photosensor 112 may includeradiation output directly from the array of light-emitting elements 112,retro-reflected radiation 134, and radiation 152 and 162 output fromother external sources 150 and 160. As such, the photosensor 112 maydetect and measure an increased radiation level higher than the actualradiation intensity or power output from the lighting device. For thecase where the photosensor measurement is input to a controller for thelighting device 100, the exaggerated measurement of the actual radiationintensity can lead to improper operation of the lighting device becausethe output radiation may not match a target or threshold radiationintensity. In other words, the radiation output from external sources(150, 160, and retro-reflected radiation 134) may act as noise obscuringmeasurement of a primary signal corresponding to the radiation 132emitted directly from the lighting device 100. Reducing incidentradiation from these external sources at the photosensor 112 can thusaid in increasing the signal-to-noise ratio, thereby increasing areliability and accuracy of the photosensor 112.

Referring now to FIG. 7, it illustrates a block diagram for an exampleconfiguration of a lighting device 700. In one example, lighting device700 may comprise a light-emitting subsystem 712, a controller 714, apower source 716 and a cooling subsystem 718. The light-emittingsubsystem 712 may comprise a plurality of semiconductor devices 719. Theplurality of semiconductor devices 719 may include a linear ortwo-dimensional array 720 of light-emitting elements such as an array ofLED devices, for example. Semiconductor devices may provide radiantoutput 724, including one or more of visible light, ultra-violet (UV)light, and infrared (IR) radiation. The radiant output 724 may bedirected to a workpiece 726 located at a fixed plane from lightingdevice 700. Returned radiation 728 may be retro-reflected back to thelight-emitting subsystem 712 from the workpiece 726 (e.g., viareflection of the radiant output 724). In some examples, the workpiece726 may include a retro-reflective surface.

The radiant output 724 may be directed to the workpiece 726 via couplingoptics 730. The coupling optics 730, if used, may be variouslyimplemented. As an example, the coupling optics may include one or morelayers, materials or other structures interposed between thesemiconductor devices 719 and workpiece 726, and providing radiantoutput 724 to surfaces of the workpiece 726. As an example, the couplingoptics 730 may include a micro-lens array to enhance collection,condensing, collimation or otherwise the quality or effective quantityof the radiant output 724. As another example, the coupling optics 730may include a micro-reflector array. In employing such a micro-reflectorarray, each semiconductor device providing radiant output 724 may bedisposed in a respective micro-reflector, on a one-to-one basis. Asanother example, a linear array of semiconductor devices 720 providingradiant output 724 may be disposed in macro-reflectors, on a many-to-onebasis. In this manner, coupling optics 730 may include bothmicro-reflector arrays, wherein each semiconductor device is disposed ona one-to-one basis in a respective micro-reflector, and macro-reflectorswherein the quantity and/or quality of the radiant output 724 from thesemiconductor devices is further enhanced by macro-reflectors. Lightingdevice 700 may further include a transparent window 764 interposedbetween the coupling optics 730 and the workpiece 726.

Each of the layers, materials or other structure of coupling optics 730may have a selected index of refraction. By properly selecting eachindex of refraction, reflection at interfaces between layers, materialsand other structures in the path of the radiant output 724 (and/orretro-reflected radiation 728) may be selectively controlled. As anexample, by controlling differences in such indexes of refraction at aselected interface, for example window 764, disposed between thesemiconductor devices to the workpiece 726, reflection at that interfacemay be reduced or increased so as to enhance the transmission of radiantoutput at that interface for ultimate delivery to the workpiece 726. Forexample, the coupling optics may include a dichroic reflector wherecertain wavelengths of incident light are absorbed, while others arereflected and focused to the surface of workpiece 726.

The coupling optics 730 may be employed for various purposes. Examplepurposes include, among others, to protect the semiconductor devices719, to retain cooling fluid associated with the cooling subsystem 718,to collect, condense and/or collimate the radiant output 724, tocollect, direct or reject retro-reflected radiation 728, or for otherpurposes, alone or in combination. As a further example, the lightingdevice 700 may employ coupling optics 730 so as to enhance the effectivequality, uniformity, or quantity of the radiant output 724, particularlyas delivered to the workpiece 726.

As a further example, coupling optics 730 may comprise a cylindricallens through which light emitted from the linear array of light-emittingelements is directed. As previously described, light emitted from thelinear array of light-emitting elements may be incident at an incidentface of the cylindrical lens, and may be collimated and redirected outof an emitting face of the cylindrical lens. The cylindrical lens mayinclude one or more of a rod lens, a semi-circular lens, a plano-convexlens, a bi-convex lens, and a faceted Fresnel lens. The cylindrical lensmay include a cylindrical lens having a cylindrical power axis and anorthogonal plano axis, for collimating and/or focusing the light emittedfrom the linear array 720 of semiconductor devices 719.

Selected of the plurality of semiconductor devices 719 may be coupled tothe controller 714 via coupling electronics 722, so as to provide datato the controller 714. As described further below, the controller 714may also be implemented to control such data-providing semiconductordevices, e.g., via the coupling electronics 722. The controller 714 maybe connected to, and may be implemented to control, the power source716, and the cooling subsystem 718. Moreover, the controller 714 mayreceive data from power source 716 and cooling subsystem 718. In oneexample, the irradiance at one or more locations at the workpiece 726surface may be detected by sensors and transmitted to controller 714 ina feedback control scheme. In a further example, controller 714 maycommunicate with a controller of another lighting system (not shown inFIG. 7) to coordinate control of both lighting systems. For example,controller 714 of multiple lighting systems may operate in amaster-slave cascading control algorithm, where the set point of one ofthe controllers is set by the output of the other controller. Othercontrol strategies for operation of lighting system 10 in conjunctionwith another lighting system may also be used. As another example,controller 714 for multiple lighting systems arranged side by side maycontrol lighting systems in an identical manner for increasinguniformity of irradiated light across multiple lighting systems.

In addition to the power source 716, cooling subsystem 718, andlight-emitting subsystem 712, the controller 714 may also be connectedto, and implemented to control internal element 732, and externalelement 734. Element 732, as shown, may be internal to the lightingdevice 700, while element 734, as shown, may be external to the lightingdevice 700, but may be associated with the workpiece 726 (e.g.,handling, cooling or other external equipment) or may be otherwiserelated to a photoreaction (e.g. curing) that lighting device 700supports.

The data received by the controller 714 from one or more of the powersource 716, the cooling subsystem 718, the light-emitting subsystem 712,and/or elements 732 and 734, may be of various types. As an example, thedata may be representative of one or more characteristics associatedwith coupled semiconductor devices 719. As another example, the data maybe representative of one or more characteristics associated with therespective light-emitting subsystem 712, power source 716, coolingsubsystem 718, internal element 732, and external element 734 providingthe data. As still another example, the data may be representative ofone or more characteristics associated with the workpiece 726 (e.g.,representative of the radiant output energy or spectral component(s)directed to the workpiece). Moreover, the data may be representative ofsome combination of these characteristics.

The controller 714, in receipt of any such data, may be implemented torespond to that data. For example, responsive to such data from any suchcomponent, the controller 714 may be implemented to control one or moreof the power source 716, cooling subsystem 718, light-emitting subsystem712 (including one or more such coupled semiconductor devices), and/orthe elements 32 and 34. As an example, responsive to data from thelight-emitting subsystem indicating that the light energy isinsufficient at one or more points associated with the workpiece, thecontroller 714 may be implemented to either (a) increase the powersource's supply of power to one or more of the semiconductor devices,(b) increase cooling of the light-emitting subsystem via the coolingsubsystem 718 (e.g., certain light-emitting devices, if cooled, providegreater radiant output), (c) increase the time during which the power issupplied to such devices, or (d) a combination of the above.

Individual semiconductor devices 719 (e.g., LED devices) of thelight-emitting subsystem 712 may be controlled independently bycontroller 714. For example, controller 714 may control a first group ofone or more individual LED devices to emit light of a first intensity,wavelength, and the like, while controlling a second group of one ormore individual LED devices to emit light of a different intensity,wavelength, and the like. The first group of one or more individual LEDdevices may be within the same linear array 720 of semiconductordevices, or may be from more than one linear array of semiconductordevices 720 from multiple lighting devices 700. Linear array 720 ofsemiconductor device may also be controlled independently by controller714 from other linear arrays of semiconductor devices in other lightingsystems. For example, the semiconductor devices of a first linear arraymay be controlled to emit light of a first intensity, wavelength, andthe like, while those of a second linear array in another lightingsystem may be controlled to emit light of a second intensity,wavelength, and the like.

As a further example, under a first set of conditions (e.g. for aspecific workpiece, photoreaction, and/or set of operating conditions)controller 714 may operate lighting device 700 to implement a firstcontrol strategy, whereas under a second set of conditions (e.g. for aspecific workpiece, photoreaction, and/or set of operating conditions)controller 714 may operate lighting device 700 to implement a secondcontrol strategy. As described above, the first control strategy mayinclude operating a first group of one or more individual semiconductordevices (e.g., LED devices) to emit light of a first intensity,wavelength, and the like, while the second control strategy may includeoperating a second group of one or more individual LED devices to emitlight of a second intensity, wavelength, and the like. The first groupof LED devices may be the same group of LED devices as the second group,and may span one or more arrays of LED devices, or may be a differentgroup of LED devices from the second group, but the different group ofLED devices may include a subset of one or more LED devices from thesecond group.

The cooling subsystem 718 may be implemented to manage the thermalbehavior of the light-emitting subsystem 712. For example, the coolingsubsystem 718 may provide for cooling of light-emitting subsystem 712,and more specifically, the semiconductor devices 719. The coolingsubsystem 718 may also be implemented to cool the workpiece 726 and/orthe space between the workpiece 726 and the lighting device 700 (e.g.,the light-emitting subsystem 712). For example, cooling subsystem 718may comprise an air or other fluid (e.g., water) cooling system. Coolingsubsystem 718 may also include cooling elements such as cooling finsattached to the semiconductor devices 719, or linear array 720 thereof,or to the coupling optics 730. For example, cooling subsystem mayinclude blowing cooling air over the coupling optics 730, wherein thecoupling optics 730 are equipped with external fins to enhance heattransfer.

The lighting device 700 may be used for various applications. Examplesinclude, without limitation, curing applications ranging from displays,photoactive adhesives, and ink printing to the fabrication of DVDs andlithography. The applications in which the lighting device 700 may beemployed can have associated operating parameters. That is, anapplication may have associated operating parameters as follows:provision of one or more levels of radiant power, at one or morewavelengths, applied over one or more periods of time. In order toproperly accomplish the photoreaction associated with the application,optical power may be delivered at or near the workpiece 726 at or aboveone or more predetermined levels of one or a plurality of theseparameters (and/or for a certain time, times or range of times).

In order to follow an intended application's parameters, thesemiconductor devices 719 providing radiant output 724 may be operatedin accordance with various characteristics associated with theapplication's parameters, e.g., temperature, spectral distribution andradiant power. At the same time, the semiconductor devices 719 may havecertain operating specifications, which may be associated with thesemiconductor devices' fabrication and, among other things, may befollowed in order to preclude destruction and/or forestall degradationof the devices. Other components of the lighting device 700 may alsohave associated operating specifications. These specifications mayinclude ranges (e.g., maximum and minimum) for operating temperaturesand applied electrical power, among other parameter specifications.

Accordingly, the lighting device 700 may support monitoring of theapplication's parameters. In addition, the lighting device 700 mayprovide for monitoring of semiconductor devices 719, including theirrespective characteristics and specifications. Moreover, the lightingdevice 700 may also provide for monitoring of selected other componentsof the lighting device 700, including its characteristics andspecifications.

Providing such monitoring may enable verification of the system's properoperation so that operation of lighting device 700 may be reliablyevaluated. For example, lighting device 700 may be operating improperlywith respect to one or more of the application's parameters (e.g.temperature, spectral distribution, radiant power, and the like), anycomponent's characteristics associated with such parameters and/or anycomponent's respective operating specifications. The provision ofmonitoring may be responsive and carried out in accordance with the datareceived by the controller 714 from one or more of the system'scomponents.

Monitoring may also support control of the system's operation. Forexample, a control strategy may be implemented via the controller 714,the controller 714 receiving and being responsive to data from one ormore system components. This control strategy, as described above, maybe implemented directly (e.g., by controlling a component throughcontrol signals directed to the component, based on data respecting thatcomponents operation) or indirectly (e.g., by controlling a component'soperation through control signals directed to adjust operation of othercomponents). As an example, a semiconductor device's radiant output maybe adjusted indirectly through control signals directed to the powersource 716 that adjust power applied to the light-emitting subsystem 712and/or through control signals directed to the cooling subsystem 718that adjust cooling applied to the light-emitting subsystem 712.

Control strategies may be employed to enable and/or enhance the system'sproper operation and/or performance of the application. In one example,the irradiance at one or more locations at the workpiece 726 surface maybe detected by sensors and transmitted to controller 714 in a feedbackcontrol scheme.

In some applications, high radiant power may be delivered to theworkpiece 726. Accordingly, the light-emitting subsystem 712 may beimplemented using an array of light-emitting semiconductor devices 720.For example, the light-emitting subsystem 712 may be implemented using ahigh-density, light-emitting diode (LED) array. Although linear array oflight-emitting elements may be used and are described in detail herein,it is understood that the semiconductor devices 719, and linear arrays720 thereof, may be implemented using other light-emitting technologieswithout departing from the principles of the invention; examples ofother light-emitting technologies include, without limitation, organicLEDs, laser diodes, other semiconductor lasers.

Continuing with FIG. 7, the plurality of semiconductor devices 719 maybe provided in the form of one or more arrays 720, or an array of arrays(e.g., as shown in FIG. 7). The arrays 720 may be implemented so thatone or more, or most of the semiconductor devices 719 are configured toprovide radiant output. At the same time, however, one or more of thearray's semiconductor devices 719 may be implemented so as to providefor monitoring selected of the array's characteristics. One or moremonitoring devices 736 may be selected from among the devices in thearray and, for example, may have the same structure as the other,emitting devices. For example, the difference between emitting andmonitoring may be determined by the coupling electronics 722 associatedwith the particular semiconductor device (e.g., in a basic form, an LEDarray may have monitoring LED devices where the coupling electronicsprovides a reverse current, and emitting LED devices where the couplingelectronics provides a forward current).

Furthermore, based on coupling electronics, selected of thesemiconductor devices in the array may be either/both multifunctiondevices and/or multimode devices, where (a) multifunction devices may becapable of detecting more than one characteristic (e.g., either radiantoutput, temperature, magnetic fields, vibration, pressure, acceleration,and other mechanical forces or deformations) and may be switched amongthese detection functions in accordance with the application parametersor other determinative factors and (b) multimode devices may be capableof emission, detection and some other mode (e.g., off) and may beswitched among modes in accordance with the application parameters orother determinative factors.

A radiation monitor 790, or radiation monitoring device, for monitoringradiation output by the lighting device 700 may include a first sensor794, a second sensor 798 and monitor electronics 790. Furthermore, theradiation monitor 790 may include a radiation filter 792. In oneexample, the radiation filter 792 may comprise a device or structurecoupled to the second sensor 798. In one example, the radiation filter792 may be coupled directly to the second sensor; in other examples, theradiation filter 792 may be coupled indirectly with the second sensor.In other examples, the radiation filter may include a structure separatefrom the second sensor that, when taken in conjunction with positioningof the second sensor, serves as a spatial radiation filter to excludethe radiation output directly from the lighting device from reaching thesecond sensor while allowing radiation output from external sources tobe received at the second sensor. In other words, the radiation filter792 may shield the second sensor 798 from the radiation output directlyfrom the light-emitting element while allowing the radiation fromexternal sources to reach the second sensor, while the radiation outputdirectly from the light-emitting element and the radiation from externalsources are incident at the first sensor 794.

Examples of the radiation filter 792 may include a mounting means forpositioning the second and/or first sensors, and light capillaries, asdescribed below with reference to FIGS. 2-6. Furthermore, shielding thesecond sensor 798 from the radiation output directly from thelight-emitting element while allowing the radiation from externalsources to reach the second sensor may be implemented by one or more ofpositioning the second sensor 798 at a non-light-emitting side of alight-emitting plane of the light-emitting element 719, supporting thelight-emitting element 719 on a base interposed between a printedcircuit board of the lighting device 700 and the light-emitting element719 to facilitate positioning the second sensor 798 at the non-lightemitting side of the light-emitting plane of the light-emitting element719, and coupling a light capillary to the second sensor 798.

As described below with reference to FIGS. 2-6, the first sensor 794 andthe second sensor 798 may include thermocouples. In another example, thefirst sensor 794 and the second sensor 798 may include photodiodes. Inother examples, first sensor 794 and the second sensor 798 may includeanother type of photosensor or radiation sensor. The radiation monitor790 may be a standalone device (as shown at the bottom of FIG. 7), andmay be retrofit to existing lighting devices for monitoring the power(or radiation intensity) output therefrom. Retrofitting the radiationmonitor 790 with a lighting device 700 may include positioning the firstsensor 794 and second sensor 798 adjacent to a light-emitting element ofthe lighting device 700. Further details regarding retrofitting alighting device with the radiation monitor 790 are described previouslywith reference to FIGS. 2-6. Additionally, the radiation monitor 790 maybe more closely integrated (as shown in FIG. 7) with a lighting deviceby conductively coupling the monitor electronics 790 with couplingelectronics 722 and/or controller 714 of the lighting device. In thisway, the lighting device operation may be modulated or controlledresponsively to measurements from the radiation monitor 790, includingresponsively to signals from the first and second sensors 794 and 798and monitor electronics 792. Non-limiting examples of retrofittingand/or integration of radiation monitor 790 with existing lightingdevices is illustrated and described above with reference to FIGS. 2-6.

For example, if the radiation monitor 790 detects a radiation outputdirectly from the lighting device that is greater than a thresholdradiation output, the controller 714 may send a signal to the couplingelectronics 722 of the lighting device 700 to reduce a power output fromthe array 720 of light-emitting elements 719. As another example, if theradiation monitor 790 detects a radiation output directly from thelighting device that is less than a threshold radiation output, thecontroller 714 may send a signal to the coupling electronics 722 of thelighting device 700 to increase a power output from the array 720 oflight-emitting elements 719. More accurate and reliable measurement ofthe radiation output directly from the lighting device 700 with theradiation monitor 790 may be further incorporated to increase anaccuracy and reliability of existing control strategies and algorithmsof the lighting device 700, as described above. In this way,discrepancies between the radiation output of the lighting device 700and a threshold or target radiation output from the lighting device 700may be reduced.

For example, the controller 714 may adjust power source 716 and/orcooling subsystem 718 in response to data received from monitorelectronics 792. In one example, a lower than threshold radiation outputmeasured by the radiation monitor 790 for a given power input from powersource 716 may indicate that the lighting device 700 may be overheated.In this case, the controller 714 may adjust cooling subsystem 718 toincrease a cooling capacity delivered to the light-emitting subsystem712 to reduce a temperature thereat. In a further example, multiplelighting devices 700 may each include integrated radiation monitors 790for measuring the radiation output therefrom and for coordinatingcontrol of both lighting systems in parallel. For example, controller714 of multiple lighting systems may operate in a master-slave cascadingcontrol algorithm, where the set point of one of the controllers is setby the output of the other controller. Other control strategies foroperation of lighting system 10 in conjunction with another lightingsystem may also be used. In another representation, controller 714 formultiple lighting systems arranged side by side may control lightingsystems in an identical manner for increasing uniformity of irradiatedlight across multiple lighting systems. In one embodiment, one set ofmonitor electronics 792 may be coupled to multiple pairs of first andsecond sensors 794 and 798 for communicating with and measuringradiation output from multiple lighting devices 700. In this way, acontroller 714 for multiple lighting devices may communicate with asingle monitoring electronics 792 for controlling the multiple lightingdevices 700, thereby simplifying controller wiring and programming.

Turning now to FIG. 2, it illustrates a partial perspective view 200 ofa lighting device, for example lighting device 700 of FIG. 7,retrofitted with a radiation monitor (e.g., radiation monitor 790 ofFIG. 7). As shown in FIG. 2, the lighting device includes an array 720of light-emitting elements 719 conductively coupled to couplingelectronics 722 (not shown in FIG. 2) of a light-emitting subsystem 712.Furthermore a controller 714 (not shown in FIG. 2) may be conductivelycoupled to the coupling electronics 722 for regulating power supplied tothe light-emitting subsystem 712. The cooling subsystem 718 may includea plurality of heat sinks 250 and 254 conductively coupled to a printedcircuit board (PCB) 210 on which the array 720 of light-emittingelements 719 is mounted. The PCB 210 may include a gold reflectivesubstrate surface layer 721 in the regions surrounding thelight-emitting elements 719 that can aid in reflecting stray radiationfrom external sources towards a direction of the radiant output 724emitted directly from the light-emitting elements. The various heatsinks 250 and 254 may be mechanically and/or conductive coupled withvarious fasteners 280 for conducting heat away from the light-emittingsubsystem 712 (including the array 720 of light-emitting elements 719)in conjunction. In the example of FIG. 2, heat sinks 250 may includefinned conductive solid structures, heat sinks 254 may include insulated(e.g., with insulation 256) cables of conductive wiring, and fasteners280 may include screws and/or bolts and/or clips for fastening the heatsinks to the printed circuit board 210.

In the example of FIG. 2, the first and second sensors 794 and 798 ofradiation monitor 790 may correspond to thermocouples 260 and 270 formeasuring radiation (radiant output 724) emitted by the array 720 oflight-emitting elements 719. The thermocouples may detect radiant output724 including radiant light energy emitted from the light-emittingelements 719 of various wavelengths and spectral distributions.Thermocouples 260 and 270 may each comprise conductive thermocouplewires 262 and 272 encapsulated along its length with concentricinsulation 264 and 274, respectively. In one example, the first andsecond thermocouples may include type-T 30-gauge thermocouples; howeverthe type of thermocouples may be selected to match a desired temperaturerange and size. Utilizing thermocouples as the first and second sensorsmay be advantageous because they may be more easily integrated orinstalled in existing lighting devices due to their small size relativephotodiodes or other optical sensors. Each of the first and secondthermocouples 260 and 270 may include uninsulated bare end sensingportions 268 and 278, respectively, for detecting and measuring infraredradiant output 724 from one or more light-emitting elements 719 of thelighting device 700. The insulation 264 and 274 may serve to thermallyand conductively insulate the thermocouple wires 262 and 272 along theirlength so that signals responsive to a measured radiant output atsensing portions 268 and 278 may be transmitted relatively unhindered tothe monitor electronics 790.

Thermocouples 260 and 270 may be positioned to be adjacent, and in closeproximity to one or more light-emitting elements 719. In one example thethermocouple 268 may be positioned so that sensing portion 268 mayreceive radiation output directly from a light-emitting element 719 ofthe lighting device 700 and external sources (including retro-reflectedradiant output) while thermocouple 270 may be positioned so that sensingportion 270 may receive radiation output from external sources withoutreceiving radiation output directly from a light-emitting element 719 ofthe lighting device 700. External sources of radiation are describedabove with reference to FIG. 1. Positioning the thermocouple 260 so thatsensing portion 268 may receive radiation output directly from alight-emitting element 719 of the lighting device 700 and externalsources may include immersing the sensing portion 268 within an emissionpath of at least one of the light-emitting elements 719 of the lightingdevice 700, as shown in FIG. 3. In the example of FIG. 2, sensingportion 268 is positioned to overhang at least one of the light-emittingelements 719 so that the sensing portion 268 is immersed within theemission path of the array 720. Immersion of the first sensing portion268 in the path of the radiation output directly from the light-emittingelement may aid in ensuring that the voltage response of the firstthermocouple 260 is principally due to the radiation output directlyfrom the light-emitting element.

Furthermore, positioning thermocouple 270 so that sensing portion 270may receive radiation output from external sources without receivingradiation output directly from a light-emitting element 719 of thelighting device 700 may include shielding the second sensor from theradiation output directly from the light-emitting elements 719. Forexample, sensing portion 278 of thermocouple 278 may be more recessedaway from the array 720 of light-emitting elements 719 relative to thesensing portion 268. In the example of FIG. 2, sensing portion 278 ispositioned in a region 228 that is at least laterally recessed away fromthe array 720 so that radiant output 724 is not directly incident on thesensing portion 278. In other examples, the sensing portion 278 may bepositioned to be vertically recessed away from the array 720, orlaterally and vertically recessed away from the array 720 so thatradiant output 724 emitted directly from the light-emitting elements 719is not directly incident on the sensing portion 278. Thus, by recessingthe second thermocouple away, the second sensing portion 268 may beexposed to radiation from external sources without being exposed toradiation directly output by the lighting device.

Positioning of the thermocouples 260 and 270 may include affixing and/orfastening the thermocouples 260 and 270 to the lighting device 700 byway of a mounting device attached to the thermocouple cladding; however,the thermocouples 260 and 270 may be mounted such that their sensingportions 268 and 278 are not in contact with other solid surfaces so asnot to bias the thermocouple measurements of radiation output directlyfrom the light-emitting elements 719 and/or measurement of radiationfrom external sources. For example, mounting blocks with a fastener maybe used to fix a position of the thermocouples 260 and 270 relative tothe light-emitting element array 720. In the example of FIG. 2, themounting device may include adhering transparent adhesive tape 240 toimmobilize and/or position the thermocouples 260 and 270 relative to oneor more light-emitting elements 719 of the array 720 such that thesensing portion 268 of thermocouple 260 receives radiation outputdirectly from at least one light-emitting element 719 and radiationoutput from external sources while the sensing portion 278 of secondthermocouple 270 receives radiation output from the external sourceswithout receiving the radiation output directly from the light-emittingelements 719 of the lighting device 700. The adhesive tape 240 mayinclude an adhesive that maintains its adhesive properties inhigh-temperature environments so that the position of the first andsecond thermocouples 260 and 270 remains reliably fixed during operationof the lighting device 700. The adhesive tape 240 as a mounting devicemay be advantageous owing to its simplicity for mounting the first andsecond thermocouples in spatially-constrained environments such as on orin proximity to PCBs. In other examples, other fastening mechanisms forfixing the position of the sensing portion 278 may be utilized, as longas they do not block radiation output from external sources from beingreceived at the second sensor. For example, relatively smallthermally-insulative block may serve as a mounting base for supportingand fixing a position of the thermocouples 260 and 270.

Positioning the sensing portion 278 in closer proximity to sensingportion 268 may increase an accuracy of the radiation monitor 790 sincethe voltage response of the sensing portions 268 and 270 to theradiation from external sources may be more nearly identical. Asdescribed previously, vertically recessing the sensing portion 270relative to sensing portion 268 may facilitate more identical mirroringof the voltage responses of the sensing portions 268 and 270 to theradiation from external sources, in spite of their verticaldisplacement. Furthermore, electronic circuitry (e.g., monitoringelectronics 792) may receive signals output from the first and secondthermocouples 260 and 270, and from those signals, determine anintensity of the radiation output directly from the light-emittingelements 719. For example, the electronic circuitry may determine anintensity of the radiation output directly from the light-emittingelements 719 based on a difference in the output signals from the firstand second thermocouples 260 and 270, respectively. In this way, theradiation monitor 790 may increase an accuracy and reliability ofmonitoring radiant output from the lighting device 700.

Referring now to FIG. 3, it illustrates a magnified partialcross-sectional view of lighting device 700, including heat sink 250,light-emitting element 719, and PCB 210 as well as first and secondthermocouples 260 and 270. As shown in FIG. 3, the light-emittingelement 719 may include a base portion 319 that raises thelight-emitting surface 322 from a plane 212 of the PCB 210 so that thelight-emitting element 719 emits radiant output 724 at a light-emittingside 312 (indicated by arrow 318) of a light-emitting plane 310. In thisway, the light-emitting plane may be roughly parallel but non coplanarwith the surface or plane 212 of the PCB 210 facing the base 319. Asdescribed above with reference to FIG. 2, adhesive tape 240 (or otherfastening means) may be affixed to both the second thermocouple 278 andthe surface or plane 212 to position the second sensing portion at anon-light-emitting side 314 of the light-emitting plane 310. In thisway, the base 319 in conjunction with the positioning of the secondsensor outside of the radiation emission field effectively enables aspatial radiation filter 792 to shield the second sensing portion 278from radiant output 724 emitted directly from the light-emitting element719 while allowing the radiation from external sources 328 to reach thesecond sensing portion 278. In the example of FIG. 3, positioning thesecond sensor outside of the radiation emission field of thelight-emitting element 719 includes positioning the second sensor at thenon-light emitting side 314 of the light-emitting plane 310. Althoughnot explicitly shown in FIG. 3, the light-emitting element 719 andlight-emitting plane 310 may be raised from the plane 212 of the PCB,and the light-emitting subsystem may include electrical connects (vias,holes, and the like) that conductively connect the light-emittingelement 719 to the circuitry electronics of the PCB 210.

The first thermocouple 260 may be positioned adjacent or in closeproximity to the light-emitting element 719 so that the sensing portion268 is positioned at the light-emitting side 312 of the light-emittingplane 310 and is immersed in the path (indicated by radiation rays 324)of the radiant output 724 output directly from the light-emittingelement. The radiation rays 324 are typically emitted within an emissionfield having an upper threshold angle of incidence of ±65 degrees,relative to the axis perpendicular to the light-emitting plane 310.Furthermore, sensing portion 268 may receive incident radiation 328 fromexternal sources, which can include radiant output 724 that isretro-reflected towards the sensing portion 268. The second thermocouple270 may be shielded from the radiant output 724 by positioning thesensing portion 278 adjacent or in close proximity to the light-emittingelement 719 so that the sensing portion 278 is positioned at anon-light-emitting side 314 of the light-emitting plane 310. In thisway, the sensing portion 278 is recessed from and shielded from theradiant output 724 output directly from the light-emitting element 719.However, equivalently to sensing portion 268, sensing portion 278 mayreceive incident radiation 328 from external sources, which can includeradiant output 724 that is retro-reflected towards the sensing portion268.

Accordingly, the sensing portion 278 may receive radiation output 328from the external sources without receiving the radiant output 724emitted directly from the light-emitting element 719 while the sensingportion 268 may receive radiation output 328 from the external sourcesand the radiant output 724 emitted directly from the light-emittingelement 719. In other words, the exposure of the first and secondthermocouples 260 and 270 to the radiation output 328 from externalsources is the same or equivalent. Furthermore, the exposure of thefirst and second thermocouples 260 and 270 to the radiation output 328from external sources may be equivalent. Receiving the same orequivalent exposure may include receiving the same radiation spectrumhaving the same intensity or irradiance at both the first and secondsensing portions 268 and 278. Further still, a measure of the actualradiant output 724 emitted directly from the light-emitting element maybe determined based on a difference between the signals output from thefirst and second thermocouples 260 and 270, as discussed below withreference to FIG. 9.

Although FIG. 3 shows the first and second thermocouples positionedadjacent to the same light-emitting element 719, above and below alight-emitting plane, respectively, in other examples, the first andsecond thermocouples may be positioned adjacent to differentlight-emitting elements 719 of the array 720, as illustrated in FIG. 2.The first and second thermocouples may be positioned adjacent todifferent light-emitting elements 719 of the array 720 in cases wherethe light-emitting elements 719 are equivalent, and/or where exposure ofthe sensing portions 268 and 278 to radiation output 328 from externalsources may be equivalent. In this way, the exposure of the sensingportions 268 and 278 to radiation output 328 from external sources maybe equivalent. As such, the radiation output from the lighting device700 may be determined by the radiation monitor 790 by subtracting theoutput signal from a second sensor (e.g., the second thermocouple 270 inthe example of FIG. 2) from the output signal from a first sensor (e.g.,the first thermocouple 260 in the example of FIG. 2).

Turning now to FIG. 4, it illustrates another partial perspective view400 of lighting device 700 coupled with another example of a radiationmonitor 790. In the example of FIG. 4, the radiation monitor 790includes a first photodiode 460 and a second photodiode 470corresponding to the first sensor 794 and the second sensor 798,respectively, and first and second light capillaries 410 and 420. Thefirst and second photodiodes 460 and 470 may include an optical coatingon their incident radiation-facing surfaces to enhance theresponsiveness of the photodiodes to incident radiation over a thresholdwavelength range. For example, the threshold wavelength range may be 395nm+/−5 nm. As another example, the threshold wavelength range may be 365nm+/−5 nm. The first and/or second light capillaries 410 and 420 maycorrespond to the radiation filter 792, which may shield the secondphotodiode 470 from the radiation output directly from thelight-emitting element 719 while allowing the radiation from externalsources to reach the second photodiode, while the radiation outputdirectly from the light-emitting element 719 and the radiation fromexternal sources are incident at the first photodiode 460.

Conventional solid transmissive light capillaries such as opticalfibers, include refractive materials such as polycarbonate, quartz,glass, and the like, so that visible light may be transmitted by way oftotal internal reflection, thereby mitigating reflective losses, ascompared to reflective light capillaries such as those constructed ofstainless steel and aluminum. Furthermore, solid transmissive lightcapillaries including those made of fused quartz and fused silica maytransmit UV radiation by way of total internal reflection. However,optical fibers are typically limited in size, having core diameters lessthan 1 mm, and consequently can have smaller light collection apertures(often less than 20°, depending on the refractive index of the fibercore material relative to the ambient environment and the claddinglayers surrounding the optical fiber). Transmissive light capillaries orwaveguides are costlier as compared to reflective light capillaries suchas metal tubes. Furthermore, mechanical integration of an optical fiberor other transmissive light capillary with a lighting device may bechallenging due to the smaller aperture, and lower thermal tolerance(e.g., cladding layers of an optical fiber can degrade when exposed tohigh irradiance conditions). In contrast, reflective light capillaries,while conventionally utilized for transmitting infrared (IR) radiationwhere they typically exhibit their highest reflectivity, can affordacceptable reflective and/or spectral losses associated with UV andvisible light and in some environments, can enable higher lighttransmission relative to transmissive light capillaries.

The first and second light capillaries 410 and 420 may each comprisehollow rigid tubes positioned between the array 720 of light-emittingelements 719 and the first and second photodiodes 460 and 470,respectively. Furthermore, the first and second light capillaries 410and 420 may each include reflective and smooth interior surfaces,including UV-reflective surfaces. In one example, the first and secondlight capillaries 410 and 420 may each comprise hollow metal tubes, suchas stainless steel tubes, aluminum tubes, and the like. In particular,the first and second light capillaries 410 and 420 may each comprisecapillary needles, such as 18 gauge metal dispensing needles. Capillaryneedles are typically stainless steel, and may be procured more easily;however, in the case of UV radiation monitoring, aluminum lightcapillaries may provide lower reflective losses as radiation is guidedalong the length of the light capillary to the first or second sensor.Reflective losses associated with the first and second light capillaries410 and 420 may be mitigated by reducing their overall length relativeto conventional reflective light capillaries. Furthermore electroniccircuitry may be exploited to amplify output signals from the first andsecond photodiodes 460 and 470, as further described with reference toFIG. 8. Further still, the ability to manufacture compact reflectivelight capillaries may be advantageous for their incorporation into smallsemi-conductor lighting devices. In applications where the amount ofradiation (UV, visible light) is very low, and where reflective lossesmay not be tolerable, transmissive light capillaries may be utilized inthe radiation monitor 790.

The first photodiode 460 and the second photodiode 470 may be coupled tothe lighting device 700 by way of a mounting means such as mountingblock assembly 450. In the example of FIG. 4, the mounting blockassembly 450 also supports and positions first and second lightcapillaries 410 and 420, respectively, relative to the first and secondphotodiodes 460 and 470, and relative to the light-emitting elements719. The first and second light capillaries 410 and 420 may each includea first opening (414 and 424, respectively, as shown in FIG. 5) at afirst end adjacent to (and more proximal to) and facing toward the firstand second photodiodes 460 and 470, respectively, and a second opening(412 and 422, respectively) at a second end adjacent to the array 720 oflight-emitting elements 719, more distally located relative to the firstand second photodiodes 460 and 470, respectively. The second openings412 and 422, respectively, may be positioned non-adjacently at thesecond end and may both face away from the first and second photodiodes460 and 470, respectively. In this way, the first and second lightcapillaries may guide radiation, including UV light, incident at thesecond openings 412 and 422 to the first and second photodiodes 460 and470, respectively. In other words, UV light incident at the secondopenings 412 and 422 may be reflected once or multiply from the (UV-)reflective interior surface as it is transmitted along the interiorlength of the first and second capillaries 410 and 420, respectively,towards the first openings 414 and 424 prior to reaching the first andsecond photodiodes 460 and 470.

More specifically, the second opening 412 of the first light capillary410 may be angled to face towards the array 720 of light-emittingelements 719 so that radiation emitted directly from light-emittingelements 719, including light rays 402, may be incident at the secondopening 412. Furthermore, radiation from external sources such asexternal source radiation 408 and retro-reflected radiation 404 from areflective surface 490, may also be incident at the second opening 412.Accordingly, both radiation emitted directly from radiant output 724 andradiation from external sources, including retro-reflected radiation,may be guided by the first light capillary 410 to the first photodiode460. In contrast, the second opening 422 of the second light capillary420 may be angled to face away from the array 720 of light-emittingelements 719 so that radiation emitted directly from the light-emittingelements 719, including light rays 402, will not be incident at thesecond opening 422. However, as shown in FIG. 4, radiation from externalsources such as external source radiation 408 and retro-reflectedradiation 404 from a reflective surface 490, may be incident at thesecond opening 422. Accordingly, the second light capillary 420 mayserve as a radiation filter 792, wherein the second light capillaryguides radiation from external sources, including retro-reflectedradiation to the second photodiode 470, or while excluding radiationemitted directly from the light-emitting elements 719 (including lightrays 402) from reaching the second photodiode 470. In this way, thesecond light capillary may act as a directional radiation filter forexcluding the radiation output directly from the light-emittingelements, thereby shielding the second photodiode 470 from the radiationoutput directly from the light-emitting elements. The first and secondlight capillaries 410 and 420 may further serve to thermally isolate andshield the first and second photodiodes 460 and 470, respectively, fromheat generated at the array 720 of light-emitting elements 719, whichmay aid in prolonging an operational life of the photodiodes.

Turning now to FIG. 5, it illustrates a magnified perspective view 500of a partially disassembled mounting block assembly 450, including amounting block 451 and a sensor-circuitry portion 453. The mountingblock assembly may be mechanically coupled to the lighting device byaccommodating a fastener such as a screw, bolt, or the like by way of afastening hole 442. Additionally, non-adhesive bonding techniques may beemployed to attach the first and second light capillaries 410 and 420 tothe mounting block 451 and to further secure the mounting block 451 tothe PCB 210. First and second photodiodes 460 and 470 may electricallyintegrated with electrical circuitry 494 of a printed circuit board 496that is mounted on a substrate 454 attached to a mounting plate 456(shown in FIG. 4). Electrical wiring 480 may be electrically andmechanically coupled to the electrical circuitry 494 and substrate 454,respectively, by way of fasteners 492. The electrical wiring 480 maysupply power to and transmit signals from the first and secondphotodiodes 460 and 470 and electrical circuitry 494. Furthermore, theelectrical wiring may be sheathed in an insulated covering, forming asheathed cable 458.

A radiation barrier 452 may be interposed between the first and secondphotodiodes 460 and 470 for reducing mixing and/or cross-contaminationof radiation (UV or other radiation) from the first light capillary 410and radiation (UV or other radiation) from the second light capillary420 prior to reaching the first and second photodiodes 460 and 470,respectively. In other examples, the first and second photodiodes 460and 470 may be positioned farther away from each other than depicted inFIG. 5, and may or may not be mounted on the same printed circuit board,for example, to accommodate the spatial layout of components in aparticular lighting device. Spacing the first and second photodiodes 460and 470 farther way from each other, and/or mounting them on separateprinted circuit boards may also aid in reducing signal mixing orcontamination arising from overlap of reflected and incident radiationafter exiting the first and second light capillaries and prior to beingreceived at the photodiodes. First and second photodiodes 460 and 470may further comprise an optical coating for increasing sensitivity andresponsiveness of photo-sensors. For example, the first and secondphotodiodes 460 and 470 may include UV-enhanced photodiodes.

Mounting block assembly 450 further includes a rigid mounting block 451,and may include a light capillary supporting portion 444, a mountingblock fastening portion 448, and a sensor mounting portion 446. As shownin FIG. 5, the sensor mounting portion 446 is positioned between andjoins the light capillary supporting portion 444 with the mounting blockfastening portion 448. Mounting block 451 may be molded or formed froman insulating (electrically non-conductive), rigid material with lowthermal conductivity, such as a thermally resistive plastic, to includelongitudinal holes (with openings facing toward the first and secondphotodiodes concentric with first openings 414 and 424) for positioningthe first and second light capillaries 410 and 420, fastening hole 442,and a sensor mounting cavity 430 within a photodiode facing surface 428of the sensor mounting portion 446. One example of a thermally resistiveplastic is polyetherimide, such as Ultem.

As shown in FIGS. 4 and 5, the first and second photodiodes 460 and 470and the radiation barrier 452 may protrude from the surface of theprinted circuit board 496 so that when the sensor-circuitry portion 453is coupled with the mounting block 451, the first and second photodiodes460 and 470 and the radiation barrier 452 are positioned at leastpartially in the cavity 430. In this way, the interior surfaces 428 and427 of the cavity 430 serve as additional barriers to mitigate strayradiation, external from radiation emitted from the first openings 414and 424, from being incident at the first and second photodiodes 460 and470, respectively. Furthermore, when the sensor-circuitry portion 453 isassembled and coupled with the mounting block 451, the first and secondphotodiodes 460 and 470 may be aligned with the first openings 414 and424, respectively, so that radiation emitted from the first openings 414and 424 is directly incident to the first and second photodiodes 460 and470. Accordingly, the first and second light capillaries 410 and 420 maybe indirectly coupled to the first and second photodiodes 460 and 470because the first and second light capillaries 410 and 420 are directlycoupled to the mounting block 450, and the photodiodes 460 and 470 aredirectly coupled to the mounting block 450. Further details regardingthe alignment and spacing of the first openings 414 and 424 with thefirst and second photodiodes 460 and 470 is described below withreference to FIG. 6.

As illustrated in FIG. 13, a cross-sectional area of second openings 412and 422 may be formed by transversely cutting a cylindrical capillarytube 1310 to form an oblique cross-sectional opening, with a cutdirection along an axis (e.g., 1316 and 1318) angled (e.g., 1326 and1328) from a transverse axis 1314 perpendicular to the longitudinal axis1312 of the light capillary tube. Furthermore, when the cut direction isalong an axis with a more acute angle to the longitudinal axis 1312, across-sectional area of the opening may be increased relative to a lessacute angle. In this way a cross-sectional area of the openings 1304 and1306 may be larger than a perpendicular transverse cross-sectional area1302, such as the cross-sectional area of the first openings 414 and424, as illustrated in FIG. 5. In this way, an amount of radiation thatis incident at the second openings 412 and 422 may be increased ascompared to openings having a smaller cross-sectional area.

Moreover, a profile of the opening may be curved (resulting from acurved cutting of the tubular capillary 1310) instead of linear(resulting from a linear cutting of the light capillary), as shown at1324, to further increase an amount of radiation that is incident at theopening 1304. Furthermore, the longitudinal axis 1312 of the lightcapillaries 410 and 420 may be parallel or positioned to be angled awayfrom or towards the light-emitting plane 310 or substrate surface layer721 to further increase or decrease an amount of radiation that isincident at the second openings 412 and 422. Increasing areal collectionof incident radiation may increase collection of stray light orradiation from external sources relative to the radiation emitteddirectly from the light-emitting elements 719; however, by excluding theradiation emitted directly from the light-emitting elements 719 fromreaching the second photodiode 470, the incident radiation from externalsources may be removed by subtracting the signal output from the secondphotodiode 470 from the signal output from the first photodiode 460, asdiscussed below.

As shown in FIGS. 4, 5, and 12, the second openings 412 and 422 may beoriented such that they may be facing in opposite directions. Forexample, the opening 412 may be facing towards a plane of the array 720of light-emitting elements 719, while the opening 422 may be facing awayfrom the plane of the array 720 of light-emitting elements 719. In oneexample, the second openings 412 and 422 may be oriented so that theircross-sections are symmetric about an axis (1212 and 1222) perpendicularto the plane of the array 720 and the PCB 210, as shown in thecross-sectional view 1210. Furthermore, the orientations of the secondopening 422 may be positioned at 180 degrees relative the orientation ofsecond opening 412 such that an amount of radiation (724) outputdirectly from the light-emitting elements 719 that is excluded frombeing incident at the second opening 422 may be increased relative toother orientations, as shown in cross-sectional view 1210. Otherorientations of the openings 412 and 422 may be possible. For example,slightly angling the opening 412 so that its axis of symmetry 1212 isangled from being perpendicular to the plane of the array 720 and PCB210 may aid in increasing capturing incident light from adjacentlight-emitting elements, as shown in cross-sectional view 1220. Inparticular, slightly angling the opening 412 may aid in capturing higherangle incident radiation from neighboring light-emitting elements.Angling of opening 422 so that its axis of symmetry 1222 is angled awayfrom being perpendicular to the plane of the array 720 and PCB 210 mayaid in capturing increased amount of high-angle incident light fromexternal sources, including retro-reflected radiation. In anotherexample, angling of opening 422 so that its axis of symmetry 1222 isangled away from being perpendicular to the plane of the array 720 andPCB 210 may allow for radiation 724 directly output from thelight-emitting elements 719 to enter the opening 422; hence opening 422may preferably positioned such that its axis of symmetry 1222 remainsperpendicular to the plane of the array 720 and PCB 210.

As described previously, with reference to FIG. 3, the radiation 724output from the light-emitting elements 719 is typically emitted withinan emission field having an upper threshold angle of incidence of ±65degrees, relative to the axis perpendicular to the light-emitting plane(e.g., ±65 degrees, relative to the axis 1222). In other words, each ofthe light-emitting elements 719 may have an emission envelope spanning130 degrees centered about the axis perpendicular to the light-emittingplane. Furthermore, the second light capillary 420 may be positioned soas to be more shallowly spaced apart from the PCB 210 so that radiantoutput having relatively higher angles of incidence from light-emittingelements 719 positioned laterally farther away from the second lightcapillary 420 may not be incident at the opening 422.

Increasing a longitudinal length 408 of the light capillaries 410 and420 may increase an amount of reflective loss imparted to the radiationas it propagates towards the photodiodes 460 and 470, respectively;conversely, decreasing the longitudinal length 408 may reduce the amountof reflective loss. Similarly, increasing a diameter 1311 of the lightcapillaries 410 and 420 (and cross-sectional area of the openings 412and 422, respectively) can increase an amount of incident light receivedthereat, whereas decreasing a diameter 1311 of the light capillaries 410and 420 (and cross-sectional area of the openings 412 and 422,respectively) can decrease an amount of incident light received thereat.Accordingly the longitudinal length 408 of a light capillary may beselected based on a desired amount of reflective loss that is tolerablefor a given amount of incident light at the second opening of thecapillary, wherein the amount of incident light at the second openingcorresponds to the diameter or cross-sectional area of the capillary. Inother words, for larger diameter or larger cross-sectional area lightcapillaries, a longer light capillary may be tolerable, since the signalstrength received at the photodiode may still be high enough afterreflective losses. Similarly, a diameter or cross-sectional area of thelight capillary may be chosen to yield enough incident light so thatenough radiation is received at the photodiode after experiencing thereflective loss corresponding to the length of the capillary. In otherwords, for shorter light capillaries, smaller diameter (orcross-sectional area) light capillaries may be tolerable, since thesignal strength received at the photodiode may still be high enough fora reliably accurate radiation monitoring after reflective losses.

In general, the diameter and length of the light capillary may beselected to yield a signal strength corresponding to a photodiode signaloutput range of 0 to 5 V for a 0 to 100% intensity range of the lightingdevice 700. Furthermore, the diameter and length of the light capillarymay be selected to yield a target signal strength to noise ratio, withthe length of the light capillary influencing signal strength loss (duereflective losses), and the diameter/cross-sectional area of thecapillary influencing signal strength (amount of radiation outputdirectly from the light-emitting element incident at the capillaryopening) and the amount of noise (amount of stray light incident at thecapillary opening). Electronic circuitry parameters may also beadjusted, as described below with reference to FIG. 8, to amplify orreduce the photodiode signal output.

Turning now to FIG. 6, it illustrates comparative schematics 600 and 602showing the positioning of a light capillary 610, which may correspondto one or more of light capillaries 410 and 420, relative to an incidentradiation-facing surface 670 of a photodiode. The incidentradiation-facing surface 670 may be elevated from surface of the printedcircuit board 496, as shown in FIG. 5, although not depicted as such inFIG. 6, for illustrative purposes. Schematic 600 illustrates positioningof the light capillary 610 relative to the incident radiation-facingsurface 670 of the photodiode that results in an overfilled condition.Positioning the light capillary 610 a distance 630 from the incidentradiation-facing surface 670 results in a projected path 680 ofradiation 624 that exceeds the area of the incident radiation-facingsurface 670. For example, a diameter 682 of the projected path 680 ofradiation 624 is greater than a diameter 672 of the incidentradiation-facing surface 670. As such, changes in radiation intensityreceived at the light capillary 610 may not be detected by thephotodiode, reducing a sensitivity and accuracy of the radiationmonitor.

In contrast, schematic 602 illustrates positioning of the lightcapillary 610 relative to the incident radiation-facing surface 670 ofthe photodiode that results in an underfilled condition. Positioning thelight capillary 610 a distance 640 from the incident radiation-facingsurface 670 results in a projected path 686 of radiation 624 that fallswithin the area of the incident radiation-facing surface 670. Forexample, a diameter 688 of the projected path 686 of radiation 624 isgreater than a diameter 672 of the incident radiation-facing surface670. In other words the cross-sectional area of radiation subtending theincident radiation-facing surface 670 of the photodiode is smaller thanthe cross-sectional area of the incident radiation-facing surface 670,itself. As such, changes in radiation intensity received at the lightcapillary 610 may be detectable and by the photodiode and will result ina corresponding change in the photodiode output signal, therebyincreasing a sensitivity and accuracy of the radiation monitor.Furthermore a distance between the light capillary and the incidentradiation-facing surface below which an overfilled condition becomes anunderfilled condition may be referred to as a threshold distance.Accordingly, when the sensor-circuitry portion 453 is assembled andcoupled with the mounting block 451, the projected path of radiation atthe incident radiation-facing surface of the photodiode may correspondto an underfilled condition; in other words, a distance between thefirst opening (e.g., 414 and 424) of a light capillary (410 or 420) andthe incident radiation-facing surface of the photodiode (460 or 470) maybe less than the threshold distance.

Turning now to FIG. 8, it illustrates a circuit diagram 800 showingoperation of monitor electronics 792 for a radiation monitor 790 such asthe radiation monitor of FIGS. 4-5. As described above, the radiationmonitor collects both incident radiation directly output from thelighting device and radiation from external sources (includingretro-reflected radiation) at a first photodiode, PD_(Inc+Refl) 860(corresponding to first photodiode 460), which generates a photocurrentcorresponding to their sum, I_(Inc+Refl). Simultaneously, the radiationfrom external sources without the radiation directly output from thelighting device may be collected and measured at the second diode,PD_(Refl) 870 (corresponding to second photodiode 470), generating aphotocurrent, I_(Refl). A differential amplifier circuit 802 may beemployed to scale and/or subtract I_(Refl) from I_(Inc+Refl)differentially in order to determine and provide a reliable and accuratedirect measure of the radiation output directly from the lightingdevice. The differential amplifier circuit 802 includes a transimpedanceamplifier (TIA) 810 for the I_(Inc+Refl) signal and a separate TIA 820for the I_(Refl) signal. The TIAs 810 and 820 may convert and amplifythe photocurrents, I_(Inc+Refl) and I_(Refl), to voltages V₁ and V₂respectively, which are input to a differential amplifier 830.

The differential amplifier 830 determines the difference between the twoamplified inputs, V₁ and V₂, to arrive at the output voltage signal,V_(out). V_(out) thus represents a differential voltage signalcorresponding to the measured radiation output directly from thelighting device (radiation from external sources subtracted from thetotal collected radiation output directly from lighting device andexternal sources). The resistor, R, may be selected to scale thedifferential voltage, V_(out), appropriately to correspond to anoperational range (e.g., 0-100% of irradiance, power level, orintensity) of the lighting device output. Furthermore resistors,R_(Inc+Refl) and R_(Refl) may be selected appropriately to provideappropriate gain scaling of the voltage signals so that the calculatedvoltage differences (e.g., V_(out)=V₁−V₂ may be resolved by thedifferential amplifier 830 over a range of photocurrents I_(Refl) andI_(Inc+Refl). The differential amplifier 830 may be mounted on aseparate PCB and the TIAs 810 and 820; alternatively, they may beintegrated as part of a larger PCB assembly, for example alight-emitting diode array driver board.

In the absence of radiation from external sources (includingretro-reflected radiation), I_(Inc+Refl) would correspond to a nominalcurrent based only on the amount of radiation output directly from thelighting device, and I_(Refl) would nominally be 0, or may include avery small current (approximately 6 orders of magnitude less thanI_(Inc)) based on its proximity away from the lighting device; I_(Refl)would nominally be 0 since essentially no radiation is incident at (andgenerating photocurrent) at the second photodiode when no externalsources of radiation are present. Thus, the second photodiode responsemay be negligible.

Gain scaling may be aid in improving the radiation monitor sensitivitybecause the photocurrent generated by the external source radiation atthe second photodiode, PD_(Refl) 870, may be several orders of magnitudeless than the photocurrent generated by the radiation directly output bythe lighting device at PD_(Inc+Refl) 860. When the radiation fromexternal sources consists essentially of the retro-reflected radiation,the photocurrent I_(Refl) may be on the order of 10⁻⁶ of the value ofI_(Inc+Refl) (e.g., I_(Inc)/I_(Refl) is on the order of 10⁶). In oneexample, R_(Inc+Refl) may be adjusted to establish an upper thresholdvalue of V_(out) to correspond to 4V. Additionally and/or alternatively,the gain may be adjusted on each TIA 910 and 920 independently toachieve an output signal scaled to the corresponding output level of thelighting device. In one example, the gains on the TIAs 910 and 920 maybe independently adjusted to achieve a flat output signal scaled to thecorresponding output level of the lighting device. In this way, theinfluence of external radiation on the sensitivity, precision, andaccuracy of the radiation monitor in measuring radiation output from alighting device may be reduced.

Turning now to FIG. 9, it illustrates a circuit diagram 900 showingoperation of monitor electronics 792 for a radiation monitor 790 such asthe radiation monitor of FIGS. 2-3. As described above, the radiationmonitor collects both incident radiation directly output from thelighting device and radiation from external sources (includingretro-reflected radiation) at a first thermocouple, TC₁ 960(corresponding to first thermocouple 260), which generates an inputvoltage corresponding to their sum, V_(Inc+Refl). Simultaneously, theradiation from external sources without the radiation directly outputfrom the lighting device may be collected and measured at the secondthermocouple, TC₂ 970 (corresponding to second thermocouple 270), whichgenerates an input voltage, V_(Refl). Accordingly, V_(Inc+Refl) may beproportional to the radiation output directly from the lighting deviceand the radiation from external sources subtending TC₁, while V_(Refl)may be proportional to the radiation from external sources excluding theradiation output directly from the lighting device, subtending TC₂.

Similar to the circuit diagram 800, a differential amplifier circuit maybe employed to scale and/or subtract V_(Refl) from V_(Inc+Refl)differentially in order to determine and provide a reliable and accuratedirect measure of the radiation output directly from the lightingdevice. TIAs 910 and 920 scale and generate output voltages V₁ and V₂corresponding to V_(Inc+Refl) and V_(Refl), respectively. The outputvoltages V₁ and V₂ are then input to the differential operationalamplifier, OpAmp 930, to determine a net differential voltage signalV₁−V₂), which provides a measure of the radiation output directly fromthe lighting device when no retro-reflective radiation and radiationfrom other external sources are present. TIAs 910 and 920 may furtherprovide scaling to amplify the input voltages V_(Inc+Refl) and V_(Refl),depending on the amount of temperature change observed at TC₁ and TC₂(corresponding to IR radiation generated by the emitted radiation fromthe lighting device and/or external sources) when the lighting device isoperational, and the change in input voltages generated correspondingthereto. For example, resistance values R₁ and R₂ may be variable andadjustable so that the amount of increase in the output voltages V₁ andV₂ in the presence of retro-reflective radiation is of similar magnitudefor both TIA 910 and TIA 920. In one example, the resistance, R₁, may beselected to provide an upper threshold value for V₁ of 4V, while theresistance, R₂, may be adjusted such that the output signal V₂ changesby the same amount as V₁ in response to the radiation incident fromexternal sources.

In the absence of radiation from external sources (includingretro-reflected radiation), V_(Inc+Refl) would correspond to a nominalvoltage based only on the amount of radiation output directly from thelighting device; furthermore, V_(Refl), may still be of similar order ofmagnitude as V_(Inc) (voltage response at thermocouple due to incidentradiation directly output from lighting device) because TC₁ and TC₂ areboth receiving IR radiation from the ambient environment around themirrespective of the lighting device emissions and any external radiationsources. Consequently, the differential voltage signal, V₁−V₂, may besmall, or less than a few volts. Accordingly, an offset voltage circuit924 may be included in the monitor electronics 792 for calibrating theradiation monitor by offsetting V₂ to zero when radiation from externalsources are absent so that V₂ may be at a voltage level that isconsistent with the radiation from the external sources influencing boththermocouples TC₁ and TC₂ equivalently, and so that V_(out)=V₁−V₂ isdetermined accurately and reliably over a range of temperaturescorresponding to operation of the lighting device 700.

Turning now to FIG. 10, it illustrates voltage response plots 1010 and1030 for operating a radiation monitor 790 such as the radiation monitorof FIGS. 2-3 and 9. Voltage response plot 1010 includes trend lines forV₁ 1012, V₂ 1014, and V_(out) 1016, and corresponds to operation of theradiation monitor according to the circuit diagram 900 without theoffset voltage circuit 924. Prior to a time of 700 s, no radiation fromexternal light sources is incident at TC₂, however V₂ 1014 may have anon-zero value between 1 and 1.5 V in response to the local ambientenvironment (temperature). Between about 700 s to 1000 s, aretro-reflective radiation source is introduced, resulting in a stepchange in the voltage signals V₁ 1012 and V₂ 1014. Without the offsetvoltage circuit 924, in the presence or absence of radiation fromexternal sources, the voltage difference, V₁−V₂, may be non-zero, basedon the relative proximity of the second sensing portion 278 to the firstsensing portion.

In contrast, voltage response plot 1030 corresponds to operation of theradiation monitor according to the circuit diagram 900, including theoffset voltage circuit 924. Here, when the radiation from externalsources is absent (e.g., prior to 700 s and after 1000 s), the offsetvoltage circuit 924 is adjusted to yield a TIA output voltage V₂ 1034 ofapproximately 0 V in response to the input signal from the secondthermocouple 270. As such, the voltage difference, V₁−V₂ 1036 (with V₁1032) output from the radiation monitor 790 may be consistent with alevel of radiation from external sources influencing both the first andsecond thermocouples. Furthermore, prior to 700 s and after 1000 s,radiation from external sources is absent, with V₂˜0V and V₁−V₂approximately mirroring the voltage response of V₁ resulting from theincident radiation directly output from the lighting device at the firstthermocouple. Between ˜700 and ˜1000 s, radiation from an externalsource is introduced (e.g., retroreflective media may be positioned ˜1mm away from the first and second photodiodes), causing equivalent stepchange responses in V₁ 1032 and V₂ 1034. Because the voltage response toexternal radiation in V₂ and V₁ are equivalent, the radiation monitor790 is able to maintain an accurate and reliable measure of theradiation output directly from the lighting device 700 based on theV₁−V₂ 1036, in the presence and absence of the radiation from externalsources.

FIG. 10 further illustrates a voltage response plot 1050 for operating aradiation monitor 790 such as the radiation monitor of FIGS. 4-5 and 8,according to the circuit diagram 800, where trend lines represent V₁1052, V₂ 1054, and V₁−V₂ 1056. Prior to the time 15 min and after 20min, no radiation from external sources is present, with V₂˜0V and V₁−V₂approximately mirroring the voltage response of V₁ resulting from theincident radiation directly output from the lighting device at the firstphotodiode. Between 15 and 20 min, radiation from an external source isintroduced, causing equivalent step change responses in V₁ 1052 and V₂1054. In the example of voltage response plot 1050, a highlyretro-reflective media may be positioned ˜1 mm away from the first andsecond photodiodes, facing the light-emitting array. Because the voltageresponse to external radiation in V₂ and V₁ are equivalent, theradiation monitor 790 is able to maintain an accurate and reliablemeasure of the radiation output directly from the lighting device 700based on the V₁−V₂ 1056, in the presence and absence of the radiationfrom external sources. Thus, little deviation from steady-state isobserved in the radiation monitor's signal V₁−V₂, even in the presenceof the retroreflective media, thereby maintaining a highersignal-to-noise ratio as compared with conventional radiation monitors.

In this manner, a radiation monitor for a lighting device may comprise afirst sensor receiving radiation output directly from a light-emittingelement of the lighting device and radiation output from externalsources, a second sensor receiving the radiation output from theexternal sources without receiving the radiation output directly fromthe light-emitting element of the lighting device; and electroniccircuitry receiving output signals from the first sensor and the secondsensor and determining an intensity of the radiation output directlyfrom the light-emitting element based on a difference in the outputsignals from the first sensor and the second sensor. A second example ofthe radiation monitor optionally includes the first example and furtherincludes a radiation filter shielding the second sensor from theradiation output directly from the light-emitting element, whileallowing the radiation from the external sources to reach the secondsensor. A third example of the radiation monitor optionally includes oneor more of the first and second examples, and further includes whereinthe first sensor and the second sensor comprise thermocouples. A fourthexample of the radiation monitor optionally includes one or more of thefirst through third examples, and further includes wherein the secondsensor is positioned at a non-light-emitting side of a light-emittingplane of the light-emitting element. A fifth example of the radiationmonitor optionally includes one or more of the first through fourthexamples, and further includes wherein the radiation filter comprisesthe light-emitting element emitting radiation at a light-emitting sideof the light-emitting plane, and the second sensor positioned at thenon-light-emitting side of the light-emitting plane. A sixth example ofthe radiation monitor optionally includes one or more of the firstthrough fifth examples, and further includes wherein the first sensor isimmersed within an emission path of the light-emitting element andpositioned at the light-emitting side of the light-emitting plane. Aseventh example of the radiation monitor optionally includes one or moreof the first through sixth examples, and further includes wherein thefirst sensor and the second sensor comprise photodiodes. An eighthexample of the radiation monitor optionally includes one or more of thefirst through seventh examples, and further includes wherein theradiation filter comprises, a second light capillary, wherein a firstopening of the second light capillary is positioned adjacent to andfacing the second sensor, and wherein a second opening of the secondlight capillary faces away from the light-emitting element. A ninthexample of the radiation monitor optionally includes one or more of thefirst through eighth examples, and further includes wherein theradiation filter comprises a first light capillary coupled to the firstsensor at a first end of the first light capillary, the first lightcapillary including a first opening at a second end of the first lightcapillary, wherein the first opening faces towards the light-emittingelement.

In a first example, a radiation monitoring system for a lighting devicemay comprise a first sensor and a second sensor positioned adjacent to alight-emitting element of a lighting device, wherein the first sensorreceives radiation output directly from the light-emitting element andradiation output from external sources, the second sensor receives theradiation output from the external sources while shielded from theradiation output directly from the light-emitting element, whereinexposure of the first sensor and the second sensor to the radiationoutput from the external sources is equivalent, and electronic circuitryreceiving output signals from the first sensor and the second sensor andcalculating an intensity of the radiation output directly from thelight-emitting element based on a difference in the output signals fromthe first sensor and the second sensor. A second example of theradiation monitoring system optionally includes the first example andfurther includes wherein the electronic circuitry is conductivelycoupled with the lighting device. A third example of the radiationmonitoring system optionally includes one or more of the first andsecond examples, and further includes wherein the intensity of theradiation output directly from the light-emitting element is modulatedin response to the intensity of the radiation output directly from thelight-emitting element calculated by the electronic circuitry.

Turning now to FIG. 11, it shows a flow chart for a method 1100 ofoperating a radiation monitor 790, such as the radiation monitor ofFIGS. 2-5. One or more of the individual steps of method 1100 may beperformed as executable instructions on-board a computer controller,such as a controller for a lighting device, or a device external fromthe lighting device. Method 1100 begins at 1110 where electroniccircuitry of the radiation monitor may be coupled to a lighting device.Conductively coupling the electronic circuitry of the radiation monitorto the lighting device may include coupling the monitor electronics 792with the coupling electronics 722 of a lighting device 700. Furthermore,the monitor electronics 792 may be conductively coupled to thecontroller 714 of the lighting device 700. In this way, the operation ofthe lighting device 700 may be adjusted responsively to an output signalfrom the radiation monitor 790. For example, if the radiation monitor790 indicates that radiation output directly from the lighting device700 is above or below a threshold value by more than a thresholddifference, the controller 714 may adjust a power supplied to thelight-emitting subsystem 712 from power source 716 to reduce or increasethe radiation output from the lighting device 700, respectively.

In another example, if the power supplied to the light-emittingsubsystem 712 for generating a threshold amount of radiation outputdirectly from the lighting device 700 (e.g., as measured by theradiation monitor 790) is greater than a threshold power level, then thecontroller 714 may increase cooling supplied from the cooling subsystem718 to the light-emitting subsystem, or may indicate a faultylight-emitting element. Accordingly, by conductively coupling themonitor electronics 792 to the lighting device 700, the operation of thelighting device 700 and the radiation monitor 790 may be more closelyintegrated. In cases, where the electronic circuitry of the radiationmonitor 790 is not conductively coupled to the lighting device 700, theradiation monitor 790 may operate as a standalone measuring device, ormay output radiation measurements to a separate computer.

Next, at 1120, method 1100 may include positioning a first and secondsensor adjacent to a light-emitting element of the lighting device. Asdescribed above, the first and second sensor may include thermocouples,photodiodes, or other types of photosensors. The first and secondsensors may be equivalent sensors with respect to type, size,construction, and the like, so that a differential output signal fromthe first and second sensors may aid in determining an amount ofradiation output directly from the light-emitting element. Furthermore,the first and second sensor may be positioned adjacent to the samelight-emitting element; alternately, the first and second sensor may bepositioned adjacent to different but equivalent (e.g., equivalentintensity, size, power, and the like) light-emitting elements in alight-emitting element array. Positioning the first and second sensoradjacent to the light-emitting element may include positioning thesensors such that the radiation monitor may determine an amount ofradiation output directly from the light-emitting element as well as anamount of radiation output from external sources, includingretro-reflected radiation.

At 1130, method 1100 may include receiving radiation output directlyfrom the light-emitting element at the first sensor. For example, afirst thermocouple 760 may be positioned so that a sensing portion 768is immersed within a path of the radiation output from thelight-emitting element. In another example, a first photodiode 460 maybe positioned in conjunction with a light capillary to guide radiationoutput directly from the light-emitting element to a photosensitivesurface of the first photodiode 460. Next, at 1140, method 1100 mayinclude receiving radiation output from external sources (includingretro-reflected radiation) at the first sensor and the second sensor. Inone example, the first sensor and the second sensor may be positionedrelative to the lighting device and relative to the external sourcessuch that radiation output from external sources received at the firstsensor and the second sensor may be equivalent.

At 1150, method 1100 may include shielding the second sensor fromradiation output directly from the light-emitting element of thelighting device. As shown in FIG. 11, shielding the second sensor fromradiation output directly from the light-emitting element may includerecessing the second sensor away from a light-emitting side 312 of thelight-emitting element 719. In this way, recessing and shielding thesecond sensor may serve to filter the radiation output directly from thelight-emitting element from reaching the second sensor. Furthermore,shielding the second sensor from radiation output directly from thelight-emitting element may include positioning a first light capillaryadjacent to the second sensor and positioning a second light capillaryadjacent to the first sensor. The second light capillary may allowradiation output directly from the lighting device and radiation outputfrom external sources to be received at the first sensor.Simultaneously, the first light capillary may serve as a radiationfilter to guide radiation output from the external sources to the secondsensor while excluding radiation output directly from the lightingdevice. In this way, radiation output directly from the lighting deviceand radiation output from external sources may be received and measuredby the first sensor, while radiation output from external sources may bereceived and measured by the second sensor while excluding radiationoutput directly from the lighting device.

Next at 1160, method 1100 may include calculating radiation output fromthe lighting device from a difference in output signals from the firstand second sensors. For example, the output signal from the first sensormay represent an amount of radiation output directly from thelight-emitting element and an amount of radiation output from theexternal sources, while the output signal from the second sensor mayrepresent an amount of radiation output from the external sources whileexcluding the amount of radiation output directly from thelight-emitting element. By subtracting the signal output from the secondsensor from the signal output from the first sensor, contribution of theradiation output from external sources on the measured output signalfrom the first sensor can be negated, thereby producing a more reliableand accurate measure of the radiation output directly from thelight-emitting element.

At 1170, method 1100 may determine if the calculated radiation output,as determined by the radiation monitor from the output signal of thefirst sensor, is above or below a threshold radiation output by morethan a threshold difference. If the calculated radiation output differsfrom the threshold radiation output by more than a threshold difference,method 1100 continues at 1180 where the controller of the lightingdevice may adjust operation of the lighting device to reduce thedifference between the calculated radiation output and the thresholdradiation output. Adjusting operation of the lighting device to reducethe difference between the calculated radiation output and the thresholdradiation output may include one or more of modulating power input,cooling capacity, and the like to the lighting device For the case wherethe calculated radiation output differs from the threshold radiationoutput by less than a threshold difference, method 1100 continues at1172 where the controller of the lighting device may maintain operation(e.g., maintain power input, cooling, and the like) to the lightingdevice. After 1172 and 1180, method 1100 ends.

In this manner, the technical result of accurate and reliable monitoringof a light source is provided. In particular, the influence incidentradiation arising from external sources is removed by subtracting itscontribution from the measured radiation. Furthermore, the radiationmonitor can be implemented and customized to a particular lightingdevice or application by utilizing different types of radiation sensors.Further still, the radiation monitoring is provided without paired lightsources. In this way, costs and complexity of the radiation monitor canbe reduced, while increasing its reliability and accuracy as comparedwith conventional devices.

Accordingly, in one example, a method of measuring radiation output froma lighting device may comprise positioning a first sensor and a secondsensor adjacent to a light-emitting element of the lighting device, andreceiving radiation output directly from the light-emitting element atthe first sensor, while shielding the second sensor from the radiationoutput directly from the light-emitting element, and while receivingradiation output from external sources at the first sensor and thesecond sensor. In such an example, additionally or alternatively, anequivalent amount of the radiation output from the external sources maybe received at both the first sensor and the second. Furthermore,receiving the radiation output from the external sources mayadditionally or alternatively include receiving retro-reflectedradiation from the light-emitting element. In some examples, the methodmay additionally or alternatively comprise determining the radiationoutput from the lighting device by subtracting an output signal from thesecond sensor from an output signal from the first sensor. Furthermore,in some examples, shielding the second sensor from the radiation outputdirectly from the light-emitting element may additionally oralternatively include recessing the second sensor away from alight-emitting side of a light-emitting plane of the light-emittingelement, wherein the light-emitting element outputs radiation from thelight-emitting plane at the light-emitting side. The method mayadditionally or alternatively comprise positioning a first lightcapillary adjacent to the second sensor, wherein shielding the secondsensor from the radiation output directly from the light-emittingelement includes orienting an opening of the first light capillary awayfrom the light-emitting element thereby guiding the radiation from theexternal sources to the second sensor while excluding the radiationoutput directly from the light-emitting element. In another example, themethod may additionally or alternatively comprise positioning a secondlight capillary adjacent to the first sensor, the second light capillaryguiding the radiation from the external sources and the radiation outputdirectly from the light-emitting element to the first sensor. In any ofthe preceding examples, determining the radiation output from thelighting-emitting element further may additionally or alternativelycomprise outputting the output signal from the second sensor, the outputsignal from the second sensor corresponding to an intensity of theradiation output from the external sources, without corresponding to theintensity of the radiation output directly from the light-emittingelement.

Note that the example control and estimation routines included hereincan be used with various lighting sources and lighting systemconfigurations. The control methods and routines disclosed herein may bestored as executable instructions on-board a controller innon-transitory memory. The specific routines described herein mayrepresent one or more of any number of processing strategies such asevent-driven, interrupt-driven, multi-tasking, multi-threading, and thelike. As such, various actions, operations, and/or functions illustratedmay be performed in the sequence illustrated, in parallel, or in somecases omitted. Likewise, the order of processing is not necessarilyrequired to achieve the features and advantages of the exampleembodiments described herein, but is provided for ease of illustrationand description. One or more of the illustrated actions, operationsand/or functions may be repeatedly performed depending on the particularstrategy being used. Further, the described actions, operations and/orfunctions may graphically represent code to be programmed intonon-transitory memory of the computer readable storage medium in theengine control system.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied tovarious Lambertian or near-Lambertian light sources. The subject matterof the present disclosure includes all novel and non-obviouscombinations and sub-combinations of the various systems andconfigurations, and other features, functions, and/or propertiesdisclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

The invention claimed is:
 1. A radiation monitor for a lighting device,comprising: a first sensor receiving radiation output directly from alight-emitting element of the lighting device and radiation output fromexternal sources; a second sensor receiving the radiation output fromthe external sources without receiving the radiation output directlyfrom the light-emitting element of the lighting device; and electroniccircuitry receiving output signals from the first sensor and the secondsensor and determining an intensity of the radiation output directlyfrom the light-emitting element based on a difference in the outputsignals from the first sensor and the second sensor.
 2. The radiationmonitor of claim 1, further comprising a radiation filter shielding thesecond sensor from the radiation output directly from the light-emittingelement, while allowing the radiation from the external sources to reachthe second sensor.
 3. The radiation monitor of claim 2, wherein thefirst sensor and the second sensor comprise thermocouples.
 4. Theradiation monitor of claim 3, wherein the second sensor is positioned ata non-light-emitting side of a light-emitting plane of thelight-emitting element.
 5. The radiation monitor of claim 4, wherein theradiation filter comprises the light-emitting element emitting radiationat a light-emitting side of the light-emitting plane, and the secondsensor positioned at the non-light-emitting side of the light-emittingplane.
 6. The radiation monitor of claim 5, wherein the first sensor isimmersed within an emission path of the light-emitting element andpositioned at the light-emitting side of the light-emitting plane. 7.The radiation monitor of claim 2, wherein the first sensor and thesecond sensor comprise photodiodes.
 8. The radiation monitor of claim 7,wherein the radiation filter comprises, a second light capillary,wherein a first opening of the second light capillary is positionedadjacent to and facing the second sensor, and wherein a second openingof the second light capillary faces away from the light-emittingelement.
 9. The radiation monitor of claim 8, wherein the radiationfilter comprises a first light capillary coupled to the first sensor ata first end of the first light capillary, the first light capillaryincluding a first opening at a second end of the first light capillary,wherein the first opening faces towards the light-emitting element. 10.A method of measuring radiation output from a lighting device,comprising: positioning a first sensor and a second sensor adjacent to alight-emitting element of the lighting device; and receiving radiationoutput directly from the light-emitting element at the first sensor,while shielding the second sensor from the radiation output directlyfrom the light-emitting element, and while receiving radiation outputfrom external sources at the first sensor and the second sensor.
 11. Themethod of claim 10, wherein an equivalent amount of the radiation outputfrom the external sources is received at the first sensor and the secondsensor.
 12. The method of claim 11, wherein receiving the radiationoutput from the external sources includes receiving retro-reflectedradiation from the light-emitting element.
 13. The method of claim 12,further comprising determining the radiation output from the lightingdevice by subtracting an output signal from the second sensor from anoutput signal from the first sensor.
 14. The method of claim 13, whereinshielding the second sensor from the radiation output directly from thelight-emitting element includes recessing the second sensor away from alight-emitting side of a light-emitting plane of the light-emittingelement, wherein the light-emitting element outputs radiation from thelight-emitting plane at the light-emitting side.
 15. The method of claim13, further comprising positioning a first light capillary adjacent tothe second sensor, wherein shielding the second sensor from theradiation output directly from the light-emitting element includesorienting an opening of the first light capillary away from thelight-emitting element thereby guiding the radiation from the externalsources to the second sensor while excluding the radiation outputdirectly from the light-emitting element.
 16. The method of claim 15,further comprising positioning a second light capillary adjacent to thefirst sensor, the second light capillary guiding the radiation from theexternal sources and the radiation output directly from thelight-emitting element to the first sensor.
 17. The method of claim 13,wherein determining the radiation output from the lighting-emittingelement further comprises outputting the output signal from the secondsensor, the output signal from the second sensor corresponding to anintensity of the radiation output from the external sources, withoutcorresponding to the intensity of the radiation output directly from thelight-emitting element.
 18. A radiation monitoring system for a lightingdevice, comprising: a first sensor and a second sensor positionedadjacent to a light-emitting element of a lighting device, wherein thefirst sensor receives radiation output directly from the light-emittingelement and radiation output from external sources, the second sensorreceives the radiation output from the external sources while shieldedfrom the radiation output directly from the light-emitting element,wherein exposure of the first sensor and the second sensor to theradiation output from the external sources is equivalent, and electroniccircuitry receiving output signals from the first sensor and the secondsensor and calculating an intensity of the radiation output directlyfrom the light-emitting element based on a difference in the outputsignals from the first sensor and the second sensor.
 19. The system ofclaim 18, wherein the electronic circuitry is conductively coupled withthe lighting device.
 20. The system of claim 19, wherein the intensityof the radiation output directly from the light-emitting element ismodulated in response to the intensity of the radiation output directlyfrom the light-emitting element calculated by the electronic circuitry.